Frothed latex sponge



Patented Apr. 21, 1953 FROTHED LATEX SPONGE {.Bhonras Rogers, Jr., and Harold H. Heinernan,

,Akron, Ohio, .assi gnors to Wingfoot Corporatronllrrqn ohio, a corporation of'Delaware Drawing. Applicatignlvlarchlti,1951,

Serial No. 216,104

7 Claims. (01. n -138.8)

This invention relates' tothe manufacture of froihed te snqeg h in im o ed Ph i a properties.

Frothed latex sponge is made generally by compounding a rubber latex with various ingredients,

such assulfur, antioxidant,accelerator, and soaps,

frothing the compounded latex, and. thenadding finishing ingredients includingla dispersion of zinc, oxideanda gallant, such as a, .dispersionof sodium or 1 potassium silica-fluoride. After the froth has undergone gelation, it is vulcanized, washed, and dried. Washing the sponge with water after vulcanizationincreases the value of the sponge for use in mattresses and pillows because the washed spongehas an improved. odor and is white in zcoloriinstead. of yellow or gray.

Desirable, sponge, is, also, characterized .by its ability to remainin a fully, expanded condition after it has been compressed many times under normal cushioning use. This prope fbyis measproved when the vulcanized tra nee latex sponge is Washed with water containing an alkaline. earth oxide, hydroxide, or salt.

Treatment comprises washing the sponge in water containingthe alkaline earth oxide, hydroxide, or salt, separately, or in .admixturewith each other and hereinafter referred to as alkaline earth treating vagentor treating agent, squeezing the excess treating agent out of thesponge and drying th sp ng i th gon e qn mann The treatment may also ,comprisejmpregnating the sponge with a dilute solution and/orislurry n a he;a l-ai .itsv ea t in agen squeezing out 1 the excessliquid, washing lightly with water, squeezing utthe excesswater, .and t nying, iii-t cqnventi n l i a in Inthe continuous p rocess of manufacturing frothed, latex sponge,.,the yulcanized sponge is passed f o thewfi e cham r t r u a se of squeeze rolls. Intermediate to these rolls are located spray nozzles positioned to direct a spray ofwater onto .the surface of the sponge. The sponge absorbs. the vwater land thecwater is then removed from the sponge as it passes through the squeeze rolls which, press rnostoi the water out of New ured in terms ofperrnanent set retention. ,An-

2 th s en Th spon ha bfi nwe e af e hi cycle ha been e e a num i e The treating agent o f'th is' invention may be added to the w'ater usedjm one or'more of the spray nozzles. The sponge may be treated with water containing the treating agent or the sponge may be treated with water containing the treating agent'fcllowed by treatment with water.

.Another manner in which this invention may be applied in the sponge industry is to pass the vulcanized frothed latex sponge through water containing the alkaline earth treating agent in which the squeeze rolls are immersed. The sponge is then passed through suitable ringer rolls and/or given an additional water Wash before the sponge isfinally dried.

The alkaline earth treating agents of this invention are the alkaline earth oxides, the alkaline earth hydroxides and the alkaline earth salts.

These treating agents includelth e oxides, hy-

droxides and salts of the alkaline earth metals barium, s'trontium', calcium," magnesium and beryllium! It has been observed that the oxides, hydroxides and salts of the alkali metals such as sodium and potassium may not be used in the same manner as the present alkaline earth treati'ng agents and are not included in the present invention.

Specific alkaline earth treating agents which may be used in this invention are calcium hydroxagents may be added to the water in concentrations rangm rrom as low as .05% to as high as 25%. i It has beenlobserved that the actual .am u i. .0? a e t ret ined ieihe sponge after it has been squeezedand driedis less than".il5% base nthe w i hi fl hespen i The physical properties of anyfrothed rubber latex sponge are improved when treated in accordance with'the present invention." By thefterm i i eth drsbb r ar sub t m t Sponge made from natural rubber latex and synthetic rubberlatex, particularly syntheticrubber latex of the type resulting the polymerization of con ugat dim .hvsire ari am ,butadiene-lfi, and particularly copolymers of conjugated diene hydrocarbons, particularly butadienelfi, with other copolymerizableimonoe mers, and particularly styrene. A specific synthetic rubber latex that maybe used is "known as Example 1 (control) The compounded rubber latex used for making the frothed latex sponge in this and the following examples had the following composition based on dry weight:

Parts Natural rubber latex 100 Sulfur -4 2.25 Zenite 1.50 .50

Ethyl zimate Sym.-di-beta-naphthyl-paraphenylene diamine 1.00 Potassium oleate .60 Potassium ricinoleate .90

The rubber latex was compounded by stirring into the latex the potassium oleate and potassium a 2-roll ringer and dried for 2 hours at 220 F. dry air. The dried sponge was allowed to cool at room temperature (72 F.) for 24 hours.

Example 2 The sponge as made in Example 1 was washed 7 in a 5% barium hydroxide slurry having a pH of 13.5 and was then washed in the regular way with water. The sponge was then dried in the same manner described in Example 1.

Example 3 The sponge as described in Example 1 was washed in a 5% calcium hydroxide slurry having a pH of 12.6 and was washed with water and dried in the same manner described for Example 1.

Example 4 The sponge as described in Example 1 was washed in a 5% calcium chloride solution having a pH of 11.75 followed by washing with water and drying in the same manner as described in Example 1.

Emample 5 The sponge as described in Example 1 was washed in a saturated solution of calcium hydroxide (.185 part of calcium hydroxide per 100 parts of water). The sponge was dried in the same manner as described in Example 1.

ricinoleate which were made up as water E Z solutions. The sulfur, Zenite, and ethyl zimate 8 6 were added as 50% water dispersions. The sym- The sponge as described in Example 1 was di-beta-naphthyl-para-phenylene diamine was washed in a 5% slurry of calcium oxide foladded as a 50% water dispersion. The sulfur lowed by washing with water and drying in the is the primary vulcanization ingredient. Zenite same manner described in Example 1. is a zinc salt of mercaptobenzothiazole coated The improvement in the physical properties of with paraffin and is used as a vulcanization acthe samples of sponge made in accordance with celerator. The ethyl zimate is an ultra-accelera- Examples 2 through 6 as compared to the physitor of vulcanization. The sym-di-beta-naphcal properties of the sponge made in accordance thyl-para-phenylene diamine is an antioxidant with Example 1 are set forth in the following which inhibits oxidation of the finished sponge. table:

Table ,9 E! F15: E A a, El ES .2 F '3 mg 7:. :05 '8 an oi? 5 ,2. so as ag 5: 5 55 s e 55 w 6 o s SO 50 #5: H5 fi 50 Snap 0dr Ha; H F H iv t! H r 4 5 fie 4 5 w 5 a 4 ew -agi l 5+: .E! 5 5 B 5 5--5 a 2 35g 2 5 IE 25 a s 6: s s a: 5 a s Ex2m 1ei(0ontro1) 320 45.3 90.0 25.4 58.2 F Example2(Ba(OH)2) 370 15.6 64.8 43 95.2 25.6 79.2 30 V r ygooi $23 good. Example3(Ca(OH)2). 380 18.7 65.8 44 93.2 26.1 84.0 44.5 do Do. Example4(CaC1z) 405 26.6 56.1 24 01.2 20.5 74.2 27.6 d0 Do. Example5(Ca(OH)z) 350 9.4 62.1 37 94.0 26.2 73.0 25.5 do DO. Example6(Oa0) 365 14 60.3 33 91.2 26.3 65.0 11.7 do D0.

The potassium oleate and potass um ricinoleate The density of the sponge is determined by are frot a e s and froth stabilizers. obtaining the weight of a unit volum of the The fully compounded latex mix as described ponge and dividing the weight by the volabove was placed into a bowl and frothed by ume. For Examples 1 through 5, the density heating air into the latex with a wire whip unis expressed in pounds/mob and is .0041? til the desired froth density was obtained. The pound/inch for each sample. finishing ingredients were then added. Three The property of permanent set retention is departs of zinc oxide as a 50% water dispersion termined by placing a piece of sponge between were stirred into the froth for'one minute. 1.40 two parallel plates, squeezing the sponge to 50% parts of sodium silicofiuoride were then added of its normal thickness, retaining the sponge in as a 20% Wa er dispersion and mixed into the this compressed condition 158 F. for 22 hours, froth for one minute. The froth was poured into releasing the sponge, and allowing it to remain at an aluminum pan. The froth became gelled after 5 minutes and the gelled froth was vulcanized for 12 minutes at 15 pounds steam pressure. The sponge rubber slab was then thoroughly washed. with water heated to 120 F., squeezed through thickness of sponge beforecomp.

This test is described in Buyers Specification- Latex Foam, issued by The Rubber Manufacturers Association under the heading-Compression Set Under Constant Deflection. The higher the permanent set retention the more desirable is the sponge for commercial use.

The tensile and elongation are determined by die-cutting dumbbell-shaped samples of 2 inch break section from the sponge. The pull required to rupture the sample is calculated in pounds/square inch of original cross section. The elongation is determined in the same operation by measuring the distance the sponge is extended before rupturing. It is expressed in percent of original. For example, a sponge having 100% elongation means that a one inch piece of sponge may be stretched two inches before it breaks. The greater the tensile and elongation of the sponge, the greater is the value of the sponge. If a sponge is being used as a seat cushion, and if the tensile and elongation are not sufficiently high, tearing of the sponge may occur around the edges. This greatly decreases the life of the cushion. Also, tensile retention and elongation retention on aging are important properties of sponge. If this same sponge is being used as a seat cushion, and if after a certain period of time its tensile and elongation decrease sufliciently through normal aging, tearing of the sponge may occur and the useful life of the cushion is limited.

The accelerated aging used in the examples is that recommended by the Rubber Manufacturers Association, Inc., Buyers Specification- Latex Foam (as revised March 5, 1948). This consists of aging a suitable sample 22 hours at 212 F. in circulating dry air.

The snap of frothed latex sponge is determined by twisting a freshly cut corner of the sponge held tightly between th fingers through two complete turns, holding the sponge in this position for 20 seconds, and then allowing the sponge to snap back to its original position. The degree of speed with which the spong returns to its original position is an indication of its snap.

The odor of the sponge is determined by cutting a section of the sponge immediately after it has been dried and having a minimum of five people compare it with the control.

The improvement in the physical properties of the sponge is very significant. The original tensile and the original elongation are improved. The snap and odor are better than the control and the physical properties on aging are im proved over the control.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modificatlons may be made therein without departing from the spirit or scope of the invention.

We claim:

1. The method of improving the physical prop erties of frothed rubber latex sponge made from a latex selected from at least one of the group consisting of natural rubber latex and a synthetic rubber latex resulting from the polymerization of a conjugated diene hydrocarbon, which comprises treating the sponge with water containing a composition selected from at least one of the group consisting of an alkaline earth hydroxide, an alkaline earth oxide, and an alkaline earth salt, removing excess treating agent and drying the treated sponge whereby at least one property of the group consisting of elongation, permanent set retention, tensile, snap, and odor is improved in comparison to sponge not treated with said treating agent.

2. Method according to claim 1 in which the treating agent is calcium hydroxide.

3. Method according to claim 1 in which the treating agent is barium hydroxide.

4. Method according to claim 1 in which the treating agent is calcium oxide.

5. Method according to claim 1 in which the treating agent is barium oxide.

6. Method according to claim 1 in which the treating agent is calcium chloride.

7. The frothed rubber latex sponge made in accordance with the method of claim 1.

THOMAS H. ROGERS, JR. HAROLD H. HEINEMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,816,764 Cornic July 28, 1931 1,852,447 Chapman et al Apr. 5, 1932 2,200,850 Miserentino May 14, 1940 2,458,221 Svendsen et a1 J an. 4, 1949 2,469,894 Rogers May 10, 1949 

1. THE METHOD OF IMPROVING THE PHYSICAL PROPERTIES OF FROTHED RUBBER LATEX SPONGE MADE FROM A LATEX SELECTED FROM AT LEAST ONE OF THE GROUP CONSISTING OF NATURAL RUBBER LATEX AND A SYNTHETIC RUBBER LATEX RESULTING FROM THE POLYMERIZATION OF A CONJUGATED DIENE HYDROCARBON, WHICH COMPRISES TREATING THE SPONGE WITH WATER CONTAINING A COMPOSITION SELECTED FROM AT LEAST ONE OF THE GROUP CONSISTING OF AN ALKALINE EARTH HYDROXIDE, AN ALKALINE EARTH OXIDE, AND AN ALKALINE EARTH SALT, REMOVING EXCESS TREATING AGENT AND DRYING THE TREATED SPONGE WHEREBY AT LEAST ONE PORPERTY OF THE GROUP CONSISTING OF ELONGATION, PERMANENT SET RETENTION, TENSILE, SNAP, AND ODOR IS IMPROVED IN COMPARISON TO SPONGE NOT TREATED WITH SAID TREATING AGENT. 